Mr. Powell said that although generals in the Afghan campaign claim progress as they move into new territory, it’s hard to tell if the Taliban really is being defeated or merely is moving from one place to another.

Mr. Powell endorsed President Obama’s strategy to triple the number of U.S. forces, but he called the government of Afghan President Hamid Karzai a weak base for the military campaign.

Mr. Powell said that the generals are asking for more time but that it’s not clear whether Mr. Obama will give it to them. Mr. Obama has said he will begin withdrawing U.S. forces next summer.

As for Iran, Mr. Powell said he doesn’t think “the stars are lining up” for an attack on that country’s known or suspected nuclear sites.

Mr. Powell also said international sanctions on Iran may never persuade Iran to back off what it says is a legitimate nuclear energy program. The United States, Mr. Powell said, may have to accept that while trying to deter Iran from building or using a bomb.